Arc preventing switch



Dec. 16, 1952 A. P'. GAuvREAu ARC PREVENTING SWITCH Filed Aug. 2o, 1949 2 SHEETS- SHEET 1 Dec. 16, 1952 A. P. GAUVREAU K 2,622,172

ARC PREVENTING SWITCH Filed Aug. 2o, 1949 2` sHEETs-SHEET 2 FIG-3 FIG-4 IN VEN TOR. ALPHONSE F. GAUVREAU ATTORNEYS Patented Dec. 16, 1952 Ano PREVENTING swrrcn Alphonse P. Gauvreau, Cleveland Heights, Ohio,

assignor to Clark Controller Company, Cleveland, Ohio, a corporation of Ohio Application August 20, 1949, Serial No. 111,528

This invention relates to electric switches or circuit breakers and `more particularly to what are known as arc preventing switches.

Opening of a circuit carrying heavy current,

especially when that current is utilized in some circuit component to create an electro-magnetic eld, causes the opening contacts to become electrodes between which is produced an arc by means of which the stored energy of the magnetic iield is dissipated. `Since collapse of the magnetic eld generates high voltages across the contacts, it tends to continue current ow across the gap and to maintain the arc. When the circuit is opened suddenly and completely, enormous electrical surge pressure is developed, requiring the use of cumbersome and expensive expediente to prevent rupture in system components and safeguard against danger to personnel. Further, in certain situations, such as in aviation, considerations of weight prohibit the use of such expedients.

The present invention aims to satisfy the foregoing and other conditions by associating with the openable main switch contacts a shunt path capable of carrying substantially full load without danger, but which path includes a variable resistance together with means for retarding variation of that resistance over a period (measured, of course, in small fractions of a second) suicient to enable the magnetic field to slowly dissipate its surge energy without danger either to circuits, apparatus or personnel.

Another object of the invention is to provide improved means, operating in conjunction with switch contacts, forV temporarily shunting rcurrent flow before closure and after opening oi said contacts, and while the shunt is in operation for progressively and slowly varying the resistance therein, thus to gradually dissipate the energy and prevent damage.

Another object is to provide an improved switch mechanism including openable contacts and in-shunt therewith a carbon stack or pile, together with means for gradually varying the pressure upon the pile, and thus its resistance, during switch opening and closing movements.

Still another object is to provide improved switch mechanism of the character described in the next preceding paragraph, including means for retarding or slowing variation in the shunt pile resistance during a period sufficient toenable the stored energy of the circuit to gradually dissipate itself without dangerous arcing, upon switch opening,

Further objects of the invention in part are obvious and in part will appear more in detail hereinafter.

In the drawings, Fig. l represents a plan view of one form of mechanism embodying the invention;

Fig. 2 is a sectional elevation on the line 2 2, Fig. l;

5 Claims. (Cl. 20G-146) Fig. 3 is a sectional elevation on the line 3-"5, Fig. 1; and

Fig. 4 is a detail sectional view, on the same plane as Fig. 3, showing another form of retarding means.

Referring to Figs. 1 to 3 inclusive, the switch mechanism shown includes an insulating base I0 on which are rigidly mounted two terminal plates Il, l2 to which the lead wires are connected. These terminals cooperate with a vertically reciprocable circuit controlling bridge or contact member I3 normally biased to switchopen position by a spring I4 and advanced to switch-closed position by depression of a pivoted armature lever I5 turning upon a small shaft IB secured to the base.

To the terminal plates I'I, I2 are rigidly secured, asby doweling, two insulated porcelain posts I'I, the upper ends of which are similarly secured to an insulated support bar I8, the latter` also being secured, by connecting plate I9, to two yokes 2Q, 2| fastened to the base. Each yoke consists of two strap members cross-connected by a cylindrical rod 22, made of magnetic material and serving as the core of a coil 23. As shown in Fig. 3, each rod 22 and the two yoke straps connected to it form the body oian electro'magnet, the two poles of which cooperate with the magnetic lever armature I5, so that upon energization and deenergization of the coil the armature is attracted to and released from gap-closing relation with the magnet poles, as is usual.

A spring 24 biases the armature lever to its retracted position shown in Fig. 3.

The movable end of armature lever I5 lies above an insulated member 25 held to the bridge I3 by a pin 26 to which one end of spring I4 is attached. Above the lever, spring I4 is surrounded by an insulating sleeve 21.

Above the sleeve 21, and strung upon the rods I'I and guided by them, is a load-discharge current-conducting contact bar 28, end portions of which are adapted to be moved into and out of current-conducting contact relation with the upper one of a series of carbon plates 28 of washer form strung upon the pillars I below a shoulder Ila on said rods which prevents substantial separation between any two of the carbon plates. In the contact bar 28 is threaded a screw 3B to which the upper end of spring Id is connected.

Assuming the parts in the switch-open position shown in Figs. 2 and 3, when the coils 23 are energized the armature lever I5 moves down, turning counterclockwise in Fig. 3, its movable end depressing bridge I3 and also, through spring I4, moving downwardly the discharge plate 2t.

Before bridge member I3 closes the gap between terminal plates iI, i2, the discharge plate 28 engages the upper ones of the carbon discs of the two piles. These discs lie loosely in contact with each other and are made of high resistance material. Consequently, at the moment of contact of plate 28 with the piles, the resistance through them is high.

Armature lever I continues its downward movement, accomplished by extension of the spring I4 and the gradual application of increase ing pressure to the two piles of carbon discs. The effect is to slowly or gradually decrease the resistance through said piles until finally, just before bridge I3 reaches the terminal plates II, I2, the resistance through the carbon piles has been reduced to such an amount that the circuit through said piles, by way of discharge plate 28, is capable of carrying the current of full load without appreciable voltage drop. This has been accomplished without the production of any arc, or at least any destructive or dangerous, arc. Now, as the downward motion of armature lever I5 continues, the bridge I3 engages both of the terminal plates I I, I2, and metallically closes the circuit betwen them, said terminal plates and bridge I3 carrying the load.

The switch will remain closed so long as the coils 23 remain energized.

Upon deenergization of the coils, the switch opens, by operations as follows:`

First, as the armature lever I5 rises, bridge I3 moves out of contact with the terminal plates II, I2. But no arc is produced, because the carbon discs of the two piles are under pressure and the discharge plate 28 across the two piles, a shunt circuit around bridge I3, carries the current of the full load traversing said piles. As theA armature lever continues its upward movement.y the pressure upon the 'two carbon piles is gradually reduced, with increase in resistance, until finally the circuit is completely broken when the discharge plate moves out of contact with the upper members of the piles.

To avoid the production of any arc, upon breaking the circuit and particularly of any destructive or dangerous arc, the present switch mecha- Anism is provided with suitable means for retarding or slowing up the variation in resistance produced by relieving the pressure upon the two piles of carbon discs. Snap action, orl any sudden action comparable to it, would require dissipation of the energy of. the magnetic field at the contacts in such a short time as to produce high f potential accompanied by eroine elleet. The retarding or restraining means may be of any kind suitable f or thepurpOSe..

In Fig-v 3, I Show thepivoted end ofA armature lever l5I provided with a semicylindrioel friction drum member 3l cooperating with a flexible brake strap 32, one end of which is attached to the base, as at 33, and the opposite end of which` 4is attached to a brake lever 34 mounted therein to turn about the same shaft I6 on which the armature lever is pivoted. Brake leverI 34 is made of magnetic material and is in the form of a. lever arm working up and down in a slot extending centrally along the armature lever I5. Brake lever 34 is biased upwardly by a spring 35.

In the arrangement shown in Fig. 3, the two springs 24, 35, at their upper ends are linked to opposite ends of a lever 50 pivoted intermediate its ends, at 5 I on a part ofv frame plate I 9. While the tension of each spring may be adjusted, they are so set as, in effect, to balance each other. Thus when the tension of either spring is increased, by movement of the lever I5 or 34 to which it is connected, pivoting motion of lever .it permits the effect to be transmitted to the other spring, the tension ofwhich also increases. Thus the degree of braking eiect becomes a function of the position of lever I5, decreasing as it rises. But, when it lowers, the braking eiTect practically disappears on account of motion of lever 34 ahead of motion of lever I5.

Accordingly, with this arrangement, when the switch is inV open position and coils 23 are energized, the brake lever 34 moves down ahead of armature lever I5, because the brake lever is very light, as comparedv with lever I5. Thus, during switch closing, brake pressure is reduced or eliminated, the reason being that during switch closing there is little danger, ifany, of are production. i

Howeveiyupon. switch opening movement, when the coils 2 3 are deenergized, the brake lever 34 again moves more rapidly than armature lever I5, and in advance of movement of lever 1.5.fwraps the brake band 32 more tightly around the drum 3I and appliesl a braking effect. This` braking effect retards upward motion of i lever I5 and thus slows up the increase in resistance through the carbon piles by the reduction of pressure between the members thereof- Inl this manner, after the conta-,ct plate,` I3 has moved out of` con tact with terminal members II, I2, a definite period of time (measured infractions of a second, of course) elapses before thedischarge plate 28 moves away from the upper membersl of the two carbon piles. That period of time cient to enable any high potential which might be generated to be dissipated gradually lbefore the circuit is completely opened. Thusdangerous or destructive arcs are eliminated or prevented.

Fis. 4 illustrates another lovin,- of ineens tor reterdins movement of the armature lever l5 during switch opening movement. In t view the base again is illustrated at II)y and thearmature lever at I5- The brake lever 34. brekebeud 32 and brake drum 3I of Eig. 31, are` entirely omitted, but other parts of the mechanism may be assumed to be the same as illustrated Eig, 3.

In this arrangement two expanding and 'contracting bellows 4D, 4I are mounted on opposite sides of a plate 4.2 attached to the bose. by screws 43, Said plete bovins en opening 4,4 por., elly closed by a valve plete. 4 5 seated upwardly eetlust ie bottom of the plete by e compression spring Upon, the `lever I5 mounted. a metering: pin 41 having a tapered end 48 cooperating .e valve With e Smell operliusin the valve plate: 4.5, the upper end of .Seid pin beine threadedior vertijoal adjustment thereof with reference to leve-r Fe- 4 illustrates the parts switch open position- The metering pin is inv such position that the Ierse endof its tapered portion. nearly closes the small opening in valve plate 45. When the yactuating coils 23are energized, lever I5 is depressed. The space within both bellows is filled with any suitable fluid, either liquid or any suitable gas. When lever I5 is depressed, downward fluid ow carries with it the valve plate 45, thus suddenly and widely openingA communicationV between the upper and lower chambers. Thus, downward motion of lever I5 and closing of the switch contacts is practically unimpeded.

However, when the switch is opened, 'by deenergizingthe coils 23', a retarding effect occurs. Spring 24 urges the armature lever I5 upwardly. Subject to the force of spring 24 and the inherent sprintr action of the bellowaby whichl they tend to return to their original condition, nui-d now flows from the lower bellows back to the upper bellows. Spring 4B, along with the change in the direction of fluid pressure, causes the valve 45 promptly to seat against the partiti-on plate. Therefore, the oil flowing upwardly can reach the upper chamber only by the small oriiice in valve 45, thus retarding the ability of bellows 40 to expand upwardly and permit the lever I5 to rise. Selection of the time of delay is accomplished through proper proportioning between the sizes of ports in the plate 42 and valve 45.

The use of a metering pin with a tapered end portion, permits accurate control of the rate and manner of upward movement of lever I5.

The tapered shank of the pin projects into the orifice in valve plate 45, thereby providing but a small aperture for oil flow. By properly proportioning the taper of the metering pin the rate of upward travel may be controlled. Further, by cutting off the end of the pin at the proper point, the end of the pin ultimately will move entirely out of the orifice and allow for suddenly increased acceleration at any desired point in the range of gradual acceleration.

In both forms of the invention, the switch closes with rapid unimpeded m-otion of armature lever I5. However, before the circuit is closed magnetically by the engagement of bridge I3 with the terminal plates II, I2, a shunt circuit is established through a resistance which at first is very high and which is gradually reduced by spring pressure until it can carry substantially full load at the time when the circuit is closed metallically. During switch opening, the circuit is iirst opened by moving bridge I 3 out of contact with terminal plates I I, I2, and then the increase in the resistance o-f the shunt circuit through the `carbon piles is accomplished gradually by relief of spring pressure, and additionally delayed during a period of time suiiicient to enable the magnetic eld to slowly dissipate its energy without danger to either circuit-s, apparatus or personnel. The switch as a whole is relatively simple, involves but a few parts not likely to get out of order in service, and is quite compact.

Other advantages of the invention will be apparent to those skilled in the art.

What I claim is:

l. Arc preventing switch mechanism, comprising two pairs of cooperating relatively movable contact members connected in parallel with the members of one pair in one branch and those of the other pair in the other branch of a circuit, the members of one pair being made of relatively low resistance material and those of the other pai-r including a porti-cn made of variable relatively high resistance material, means for supporting and operating said members in such manner that upon switch opening movement the members of the low resistance pair separate first, means effective upon switch closure for reducing said variable high resistance, and means energized by movement of said switch, and responsive thereto, and effective thereon whereby to retard the rate of change of said variable high lresistance during switch opening movement.

2. Switch mechanism of the character described in claim 1, in which said variable relatively high resistance consists of a carbon pile the lresistance of which is varied by varying the pressure upon the pile.

3. Arc preventing switch mechanism, comprising two relatively low resistance terminals separated by a gap, and means for closing said gap by way of two parallel branches of a switch circuit, one branch including a relatively low resistance bridge member adapted to open the gap and contact both terminals, and the second branch including two piles of high resistance plates which respectively at one end engage said terminals, and a relatively low resistance bar adapted t-o contact the opposite ends of said piles, means for movably supporting said bridge member and low resistance bar to move together toward and from said terminals during switch closing and opening movements, yielding means between said bridge member and resistance bar compelling closure of the second branch before the rst during switch closing, and opening of the second branch after the first during switch opening, means for moving said member and bar into and out of switch closing position and for applying and relieving pressure between the high resistance plates during such motion, and means for retarding change of such pressure during switch opening movement during a period of time sufficient to permit gradual dissipation of the transient electrical surge incident to switch opening movement said retarding means being responsive to and energized by the aforesaid means for moving said member and bar.

4. Arc preventing switch mechanism comprising two terminals separated by a gap, a pivoted lever, two sets of current conducting members actuated by said lever and adapted respectively to close and open parallel paths between said terminals, one path including variable high resistance and the other low resistance members, means arranged upon switch closing to reduce the high resistance and upon switch opening to increase the high resistance, and means responsive to movement of said lever, yand effective thereon, whereby to retard the rate of increase of said high resistance by retarding switch opening movement of said lever.

5. Arc preventing switch mechanism comprising two pairs of cooperating relatively movable contact members connected in parallel with the members of one pair in one branch and those of the other pair in the other branch of a circuit, the members of one pair being made of relatively low resistance material and those of the other pair including a portion made of variable relatively high resistance material, means for supporting and operating said members in such manner that upon switch opening movement the members of the low resistance pair separate iirst, means elective upon switch closure for reducing said variable high resistance, and means energized by switch opening movement and responsive thereto, and eiiective thereon, whereby to retard the rate of increase Iof sai-d variable high resistance during such switch opening movement.

ALPHONSE P. GAUVREAU.

REFERENCES CITED The following references are of record in the iile ofA this patent:

UNITED STATES PATENTS Number 

